MICROLENS ARRAY IMAGING-SYSTEM FOR PHOTOLITHOGRAPHY

A micro-optical system is proposed that uses a stack of four microlens arrays for 1:1 imaging of extended object planes. The system is based on the concept of multiple-aperture imaging. A compact system is pres ented that is remarkable in that it provides a diffraction-limited res olution of 3 mu m for unlimited object and image areas. Resolution of 5 mu m has been demonstrated for an area of 20x20 mm(2) in an experime ntal setup using melting resist microlens arrays (190-mu m lens diamet er). The investigated imaging system was developed in connection with a new contactless photolithographic technique called microlens lithogr aphy. This new lithographic imaging technique provides an increased de pth of focus (>50 mu m) at a larger working distance (>1 mm) than with customary proximity printing. Potential applications are photolithogr aphy for large print areas (flat panel displays, color filters), for t hick photoresist layers (micromechanics), on curved surfaces (or subst rates with poor planarity), in V grooves, etc. (C) 1996 Society of Pho to-Optical instrumentation Engineers.